There is an intriguing epilogue to be added to the obituary of the distinguished Guatemalan economist, Alberto Fuentes Mohr, who was variously kidnapped, jailed and exiled as a result of his service to his native land bofore his assassination in January at age 51.

As early as 1971, Fuentos Mohr received a stark warning that those in power in Guatemala, and who considered him a dangerous leftist, intended to kill him.

"I am able to say that," he wrote a friend at the time, in a letter meant to be revealed only after his death, "because I have information given me by a ranking official of the U.S. Embassy who let his conscience be his guide."

That official, then-ambassador Nathaniel Davis, represented the very country, the United States, that Fuentes Mohr blamed for a substantial part of his nation's bloody political turmoil.

Guatemala's current fratricidal politics go back to a revolution in 1944 that threw out a dictator and then turned sharply left. The CIA stepped in with a coup in 1954 that threw a pall over efforts to build democracy, and it was only with the election of the government that Fuented Mohr served as finance minister and then foreign minister in the late 1960s that even the moderate left was allowed to participate in politics again.

But the extremists would have none of it. Marxist guerrillas machinegunned to death U.S. Ambassador John Gordon Mein. Fuentes Mohr soon was kidnapped by the same band.

Then foreign minister, he was ransomed for a captive guerrilla. His reformist government lost the next election to a colonel dedicated to repression of the left.

Soon Fuentes Mohr was jailed without charge and harassed into exile in Costa Rica. It was then that he heard from Mein's successor, Davis, of the threat to his life. Fuentes Mohr worte: "If they succeed in killing me, Guatemalans and all the world should know that it was done under the direct order of Carlos Manuel Arana Osorio," the colonel then in the presidency.

Fuentes Mohr called Arana's regime "an authentic fascist regime," sustained by the political right, the army, "the new oligarchy of millionaire gangsters headed by Anastasio Somoza" in nearby Nicaragua and "the United States through its embassy, its millitary missions and the CIA."

Still, he had a high regard for Davis, who had "let his conscience be his guide" in passing word of the threat.

As it happened, the threat to Fuentes Mohr did not materialize at that time and Arana, now a Guatemala City businessman, has in no way been implicated in his death. No one has, although he was cut down by submachine gunners in the very center of the city. A witness subsequently was assassinated.

Fuentes Mohr's widow, Shirley, a Canadian, has accused the Guatemalan government of killing her husband. Others have blamed the right-wing Death Squad terrorists who, according to a tally of the Guatemalan press, were responsible for 214 killings in the last half of 1978. Of 505 deaths listed in that period, 30 were among security forces, 13 were businessmen and virtually all the rest were what the extreme right perceives as the extreme left.

"They assassinate me," Fuentes Mohr wrote in 1971, "for the crime of wishing that human rights be respected in my country, for the crime of wanting to help eradicate the insufferable missery and terror in which the great majority of Guatemalans live."

For Fuentes Mohr, the Nicaraguan Somoza was a special symbol of this political violence that so impeded rational democratic development in Latin America. It was a measure of his frustration that, after a lifetime of counselling the United States to stay out of Latin American affairs, he finally called on the United States to cut ties with Somoza and bring him down before Nicaragua's budding civil war spread through the isthmus.

U.S. support has since been withdrawn; Somoza endures. But Fuentes Mohr's capacity for underestimating the resilience of his opponents was hardly the measure of the man. Said Ambassador Davis, now at the Naval War College, "I respected and admired him as a distinguished statesman, a man of courage, a man of the highest intellectual capacity and as an honest and honorable representative of his country...."

Fuentes Mohr's last public acts involved a spirited condemnation of violence against Guatemalan labor leaders and the formation of a Social Democratic Party. His widow has vowed to return to Guatemala, and his 27-year-old son, along with other founding members of the party, intends to make the party a living memorial to him.